I've used IfByPhone and Twilio for a little more than a year for building telephony apps that integrate with software products to improve workflows. You are looking for feedback on their virtual phone system offering which I haven't used first hand.

If your team is tech savvy, OpenVBX from Twilio (http://www.twilio.com/api/openvbx) might be a good option.

You might want to check www.phonebooth.com as well.

Good luck!

@awaz - What was your business use case for Ifbyphone?

What exactly are your business needs?

If you need an IVR or virtual call center, the ability to measure response rates from ads, or the ability to automate notification calls to your customers, then Ifbyphone would be an excellent fit. Tell us more about your business and your needs, and we can help you figure our what makes the most sense for you.

I'm actually not a customer. I'm a competitor. Pleasure :)

I really wanted to like RingCentral since the price was pretty good, it has lots of features and the UI was pretty easy. But the reliability was marginal (once monthly extended outages; random call drops). This was over a year ago so it's distinctly possible that reliability has improved.